1. Field of the Invention
The present invention relates to an adapter for a DC power source unit that converts AC voltage from a commercial power source into DC voltage, the adapter supplying the DC voltage to a cordless power tool.
2. Description of the Related Art
Battery packs normally include a plurality of 1.2V cells connected together to produce a voltage of 9.6V, 12.0V, 14.4V and the like, to match the rated voltage of a power tool. Because the number of connected cells varies with the type of battery pack, the different battery packs have different external shapes.
FIGS. 1(a) to 3(b) show examples of battery packs. FIGS. 1(a) and 1(b) are plan and side views, respectively, showing a battery pack 28 with eight 1.2V cells connected together to produce a 9.6V output. FIGS. 2(a) and 2(b) are plan and side views, respectively, showing a battery pack 29 with ten 1.2V cells connected together to produce a 12.0V output. FIGS. 3(a) and 3(b) are plan and side views, respectively, showing a battery pack 30 with twelve 1.2V cells connected together to produce a 14.4V output.
As shown in FIGS. 1(a) and 1(b), the 9.6V battery pack 28 includes a fitting portion 28a. The fitting portion 28a includes a protruding portion 28b and a groove 28c. The fitting portion 28a is adapted to fit into a battery holding space of a power tool (not shown) with a rated voltage of 9.6V (referred to as 9.6V power tool herein after). The battery holding space includes a groove portion that engages with the protruding portion 28b, and a protruding portion that engages with the groove 28c, when the fitting portion 28a is properly inserted into the battery holding space.
The 12.0V battery pack 29 shown in FIGS. 2(a) and 2(b) is provided with a fitting portion 29a. The fitting portion 29a includes a protruding portion 29b with the same shape as the protruding portion 28b of the battery pack 28. Although not shown, a battery holding space of a 12.0V power tool is provided with a groove portion that engages with the protruding portion 29b when the fitting portion 29a of the battery pack 29 is properly inserted into the battery holding space.
When a user attempts to insert the 12.0V battery pack 29 into the 9.6V power tool, the upper end of the fitting portion 29a will abut against the protruding portion provided in the battery holding space of the 9.6V power tool, so that the fitting portion 29a can not be properly inserted into the battery holding space. Because improper 12.0V voltage will not be supplied to the 9.6V power tool, the life of the power tool will not be reduced by improper voltage supply. It should be noted that there is little risk of reducing the life of the 12.0V power tool by driving the 12.0V power tool using the 9.6V battery pack 28. Therefore, the fitting portion 28a of the 9.6V battery pack 28 is configured so that it can be inserted into the battery holding portion of the 12.0V power tool.
Further, as shown in FIGS. 3(a) and 3(b), the 14.4V battery pack 30 includes an fitting portion 30a. The fitting portion 30a has a protruding portion 30b provided at a different position than of the protruding portions 28b, 29b of the battery packs 28, 29. Although not shown, the battery holding space of a 14.4V power tool is provided with a groove portion that engages with the protruding portion 30b when the fitting portion 30a of the battery pack 30 is inserted into the battery holding space of the 14.4V power tool.
With this configuration, when a user attempts to insert the 14.4V battery pack 30 into the 9.6V power tool or the 12.0V power tool, the protruding portion 30b of the battery pack 30 will abut against the lower edge of the battery holding space of the power tool, so that the fitting portion 30a can not be inserted into the battery holding portion. Similarly, when a user attempts to insert the 9.6V battery pack 28 or the 12.0V battery pack 29 into the 14.4V power tool, the protruding portion 28b or 29b of the battery packs 28, 29 will abut against the lower edge of the battery holding space of the 14.4V power tool, so that the fitting portion 28a or 29a of the battery packs can not be inserted into the battery holding space.
Note that the battery packs 28, 29, 30 are formed with protruding portions 28b, 29b, 30b on only one side of the fitting portions 28a, 29a, 30a. With this configuration, the fitting portions 28a, 29a, 30a can not be inserted in the battery holding portions with polarities reversed, even into a power tool with the corresponding rated voltage.
The battery packs 28, 29, 30 are provided with latches 31, 32 that engage with corresponding engagement portion (not shown) of the power tools, and fix the battery packs 28, 29, 30 in the, power tools, when the fitting portions 28a, 29a, 30a are properly inserted into the battery holding spaces of the power tools.
As shown in FIGS. 1(a) to 2(b), the 9.6V and 12.0V battery packs 28, 29 both have a latch 31 with the same shape and provided at substantially the same position. A protrusion 29c is provided near the latch 31 of the battery pack 29.
Although not shown in the drawings, the 9.6V and 12.0V power tools are provided with an engagement portion that engages with the latch 31 when the fitting portion 28a, 29a of the battery pack 28, 29 is properly inserted into the battery holding space of a power tool that has a rated voltage that matches the output voltage of the battery pack 28, 29. The 12.0V power tool is also provided with a groove portion adjacent to the engagement portion that engages with the latch 31. This groove portion matches the protruding portion 29c. With this configuration, the power packs 28, 29 can be attached to the corresponding power tools.
Because the battery pack 29 is provided with the protruding portion 29c, even if the fitting portion 29a is somehow actually inserted into the battery holding space of the 9.6V power tool, the protruding portion 29c will abut against the lower edge of the power tool. This prevents the latch 31 and the engagement portion of the power tool from engaging together, so the battery pack 29 can not be properly mounted. It should be noted that it is possible to mount the 9.6V battery pack 28 into the 12.0V power tool.
As shown in FIGS. 3(a) and 3(b), the latches 32 of the 14.4V battery pack 30 are provided at two positions, both different from the latches 31 of the battery packs 28, 29. That is, the latches 32 are provided at two opposite sides of the battery pack 30, whereas the latches 31 are provided at a single front surface of the battery packs 28, 29. Accordingly, the 14.4V power tool is provided with two engagement portions at opposing sides thereof, for engaging with the latches 32 when connected to the battery pack 30.
Because the 14.4V battery pack 30 has latches 32 positioned at different locations than the latches 31 of either the 9.6V battery pack 28 or the 12.0V battery pack 29, even if somehow the fitting portion 30a of the battery pack 30 is actually inserted into the battery holding space of the 9.6V power tool or the 12.0V power tool, the latch could not possibly engage with the engagement portion of the power tool, so the battery pack 30 could not be properly mounted. Also, even if the 9.6V battery pack 28 or the 12.0V battery pack 29 were somehow inserted in the 14.4 power tool, the latch 31 could not be engaged with engagement portion of the 14.4 power tool.
By designing the power tools and the battery packs 28 to 30 in this manner, the fitting portion of a battery pack can not be inserted into the battery holding space of a power tool when the battery pack has a larger or different output voltage than the rated voltage of the power tool. Also, a battery pack can not be properly attached to a power tool when the battery pack has an output voltage that is larger or different from the rated voltage of the power tool. With this configuration, battery packs are prevented from being used with power tools when the battery packs have larger or different output voltage than the rated voltage of the power tool. This prevents related reduction in the life of the power tool and decrease in efficiency.
FIG. 4 shows an example of a conventional DC power source. The DC power source includes a main body 1, an adapter 200, and a power cord 4. The adapter 200 includes a connecting cord 300 that is connected at one end to the main body 1.
The adapter 200 has the same shape as the battery pack (not shown) that corresponds to a power tool 33, so that the adapter 200 can be mounted in the power tool 33. The main body 1 outputs a DC voltage that is supplied to the power tool 33 through the connecting cord 300 and the adapter 200.
The battery holding space of the power tool 33 has a shape that depends on the rated voltage of the power tool 33 in the manner described above. Therefore, a plurality of adapters 200 are provided, each matching the shape of the battery holding space of a power tool 33 with a different rated voltage. For example, the adapter 200 for a 9.6V power tool 33 has the same shape as the 9.6V battery pack 28, and the adapter 200 for a 14.4V power tool 33 has the same shape as the 14.4V battery pack 30. Once the proper adapter 200 is inserted into the corresponding power tool, the user sets the output voltage from the main body 1 according to the rated voltage of the power tool 33.
In this way, the conventional DC power source is provided with a plurality of different adapters 200, each corresponding to a power tool 33 with a different rated voltage. The different adapters 200 and the output voltage from the main body 1 are selected according to the power tool 33 that the DC power source is used with. For this reason, in order to use a power tool 33 with a different rated voltage, the output voltage from the main body 1 must again be set and the adapter 200 connected to the main body must also be switched. This operation is complicated. Also, the user must carry around a plurality of adapters 200, which is troublesome and inefficient.
It is an objective of the present invention to overcome the above-described problems, and provide a single adapter that can supply DC voltage from a DC voltage source to a plurality of power tools with different rated voltages.
In order to achieve the above-described objective, an adapter according to one aspect of the present invention includes a cord, a fitting portion, a voltage setting unit, and a fitting prevention mechanism. The cord is adapted to connect to a DC power source unit in order to receive DC voltage from the DC power source unit. The fitting portion is for insertion into the battery holding space of any one of a plurality of cordless power tools. The fitting portion receives the DC voltage received through the cord and supplies the DC voltage to a cordless power tool in which the fitting portion is properly inserted. The voltage setting unit is for setting voltage supplied through the fitting portion to the cordless power tool. The fitting prevention mechanism operates in linked association with operation of the voltage setting unit to prevent proper insertion of the fitting portion into a cordless power tool that has a rated voltage different from the voltage set by the voltage setting unit. With this configuration, the same adapter for a DC voltage power source can be used with power tools having different rated voltages.
An adapter according to another aspect of the present invention includes a cord, a fitting portion, and a mounting mechanism. The cord is adapted to connect to the DC power source unit in order to receive DC voltage from the DC power source unit. The fitting portion is for insertion into the battery holding space of any of the cordless power tools. The fitting portion receives the DC voltage received through the cord and supplies the DC voltage to a cordless power tool in which the fitting portion is properly inserted. The mounting mechanism is adapted for engaging with a portion of any one of at least two cordless power tools having different rated voltages. With this configuration, the same adapter for a DC voltage power source can be used with power tools having different rated voltages.